Some glass articles for automotive and architectural uses have conductor wires formed thereon as defoggers in order to ensure visibility. Further, rear and side windows for automotive vehicles are sometimes equipped with glass antennas. The glass antennas have respective patterns of conductor wires, called “antenna patterns”, formed on surfaces of glass plates.
These conductor wires are connected to metal terminals for power supply (referred to as “power supply terminals”). The power supply terminals are conventionally joined to glass parts by lead-containing solders. However, lead is generally a highly toxic environmental pollutant substance so that the influences of lead on the health and environment, notably the deleterious effects of lead on the ecosystem and the pollution of the ecosystem by lead, are becoming a matter of concern. In particular, there is a concern that, in the case where glass articles with lead-containing solders are thrown out as waste, lead may be eluted into the environment upon adhesion of acid rain etc. to these solders.
The use of lead-free solders in electronic boards has thus been spreading rapidly in the home-appliance industry. However, solders for joining glass parts and metal terminals are required to achieve a higher level of joint strength than those of solders for electronic boards and are likely to cause, in response to sudden temperature changes, problems such as deterioration in joint strength and cracking of glass surface by concentration of stress on the solder joints between the glass parts and the metal terminals due to difference in thermal expansion coefficient between glass and metal.
A Sn-3Ag-0.5Cu solder alloy (Sn-based solder alloy containing 3 mass % of Ag and 0.5 mass % of Cu) is currently used as the mainstream of the lead-free solder for electronic boards and regarded as one of reliable solder alloys because of its high joint strength on electronic boards (see Patent Document 1).
There are also known various solder alloys such as Sn—Zn—Bi alloy (see Patent Document 2) and Sn—In—Ag alloy (see Patent Document 3) for electronic boards.